The present invention relates to the field of form, fill and seal packaging systems, and more particularly, to an improved product stripper/bag sealing operation and/or bag film feeding operation that may be used in conjunction therewith, and all of which may be computer controlled for forming different size bags for maximum packaging speed.
Machines and related methods for forming, filling and sealing of packages made from a continuous film are widely used to package a variety of loose products, such as snack foods, frozen foods and the like. These machines typically comprise a supply of packaging film in the form of a web, a former for converting the web of film into a continuous hollow tube and reciprocating jaws for stripping, sealing and cutting the tube into a consecutive series of filled packages, sometimes referred to as pillow-shaped bags. One of the most successful approaches for stripping/sealing calls for mounting of the reciprocating stripping/sealing jaws on a carriage that is driven for movement in the direction of the bag forming.
The sealing jaws in this typical packaging machine/method are brought together in two steps. The first step closes the jaws just sufficiently to bring the stripper plates, which are mounted below the sealing jaws, into engagement to flatten the package film tube. The stripper plates are moved in the longitudinal direction along the tube and relative to the film in order to strip any product from the zone of the tube to be subsequently sealed. The second step completes the closing of the bag by bringing the sealing jaws together to form the seal and to cut the leading bag from the tube.
After each bag is formed, the jaws are typically moved away from the film tube and in the reverse feed direction back to the home position in readiness for producing the next bag from the continuous film tube.
One of the primary areas of recent development in packaging for today's snack food industry is machine enhancement for increased speed of operation of this type of form, fill and seal packaging system. With the increased speed, there is also a demand among users for the machine to be even more efficient in terms of energy use and machine reliability. In response to these demands, new systems for improved feeding of the packaging film by the use of computer controlled stepper motors has been developed, as set forth in the U.S. Pat. No. 4,727,707, issued Mar. 1, 1988, and assigned to the same assignee as the present invention. The feeding of the film is maximized in terms of speed and efficiency and can be controlled in order to adapt the machine for an infinite variety of bag sizes. The film feed is maximized further in terms of speed and efficiency by constantly accelerating the film over the first half of the driving time and constantly decelerating the film over the remaining half. These features, along with others, provide a substantial amount of the increase in the efficiency and speed of the operation and, indeed, have been effective in obtaining substantial acceptance among the industry. The endless belt/stepper motor film drive is employed as the preferred approach in the present invention also.
In order to obtain even greater film feeding efficiency and speed, the next step turned out to be controlling the in and out movement of the stripper and sealing jaw apparatus on the machine. There has now been a successful approach for increasing the machine speed by limiting this movement to just the amount needed for a particular bag size. By use of a preferred servo motor and programmable index controller circuit, the packaging machine can be programmed to operate at the increased speed and efficiency over a broad range of bag sizes. In essence, the stripper/sealing jaws move with respect to the film tube only in the amount necessary to perform their operation on that particular bag and, thus, eliminate all unnecessary movement. This, in effect, compresses the time cycle for packaging. Furthermore, this has been accomplished for a new minimum cost of manufacturing while assuring the lowest energy cost and greatest reliability. This apparatus/method is disclosed and claimed in prior U.S. Pat. No. 4,751,808.
Many in the industry feel that with the development of the improved packaging operation brought about by the two foregoing advances in the art that the optimum operation speed and efficiency has finally been attained. However, I have recently discovered that additional advances are possible in the area of stripping/sealing of the bag as it is formed. More specifically, the improvement is possible in the area of controlled driving of the movable carriage which performs the stripping and sealing operation. Furthermore, my discovery has included using the movable carriage for assisting the bag filling function which has heretofore not been considered or discovered.